Production of lubricating oils

ABSTRACT

Lube oils of improved viscosity index are prepared by hydrocracking a heavy oil charge stock, separating the lube oil portion of the product into a light cut and a heavy cut, extracting aromatics from the heavy cut, combining the extracted aromatics with the light cut and hydrogenating the mixture. The products may be used separately or the hydrogenated mixture may be combined with the extracted heavy cut.

United States Patent [191 [111 3,923,636

Mead et al. 1 Dec. 2, 1975 [541 PRODUCTION OF LUBRICATING OILS 3,702,817 ll/l972 Cummins et al 208/87 3,870,622 3/1975 Ashton ct al. 208/93 [75] Inventors: Mead Arthur; 3.876.522 4 1975 Campbell 6t al 2.08/58 Norman R. Odell, Nederland; John it' f Houston of Primary ExaminerDelbert E. Gantz Assistant Examiner-G. E. Schmi'tkons [73] Assignee: Texaco Inc., New York, NY. Attorney, Agent, or FirmT. H. Whaley; C. G. Ries; 22 Filed: June 3, 1974 Rbert Knox [21] Appl. No.: 475,485 [57] ABSTRACT Lube oils of improved viscosity index are prepared by 2% 9 2 hydrocracking a heavy oil charge stock, separating the 'T C 0 37/06 C10 H0O lube oil portion of the product into a light out and a l 0 Search 2 8 96 heavy cut, extracting aromatics from the heavy cut, combining the extracted aromatics with the light cut [56} References Cited and hydrogenating the mixture. The products may be UNITED STATES PATENTS used separately or the hydrogenated mixture may be 3,189,540 6/1965 Kozlowski et al 208/264 combined with the extracted heavy cut. 3,579,437 5/1971 Wentzheimer 208/87 3.666657 5/1972 Thompson et al. 208/58 9 Clam, N0 Drawmgs PRODUCTION OF LUBRICATING OILS This invention relates to the production of lubricating oils. More particularly, it is concerned with the production of lubricating oils of high viscosity index in improved yields from low quality stocks.

Due to the increasing demand for petroleum products, particularly lubricating oils, the supply of crude oils of good lubricating properties such as Pennsylvania crude is not nearly sufficient to meet the demand. It has now therefore become necessary to produce lubricating oils from low quality stocks which ordinarily would be converted into products less valuable than lubricating oils. It has already been proposed to convert low quality heavy oils into lubrioils of high visocisty index by a procedure involving hydrocracking, solvent refining and dewaxing but although this procedure is successful in producing oils of improved quality, the yield of product is unsatisfactorily low. We have now discovered a process for the production of lubricating oils of high viscosity index in improved yields.

According to our invention, a heavy oil charge stock is subjected to catalytic hydrocracking, a lubricating oil fraction is recovered from the hydrocracked product, the hydrocracked lubricating oil fraction is then fractionated into a light lube oil out and a heavy lube oil cut, the heavy cut is treated with a solvent having an affinity for aromatics to produce an aromatic-poor raffi nate and an aromatic-rich extract, the extract is combined with the light lube oil out and the mixture subjected to hydrogenation. The hydrogenated oil may be used per so as a lubricating oil or may be combined with the aromatic-poor raffinate.

The charge stocks for the process of our invention may ordinarily be residua or heavy distillates such as vacuum residua or paraffinic distillates or naphthenic distillates of which a considerable portion boils above about 950F. Advantageously, the residual fractions are subjected to a deasphalting procedure such as treatment with a low molecular weight paraffin such as propane or butane to remove the asphalt-prior to hydrocracking.

The hydrocracking catalyst used in the hydrocracking step of our novel process generally comprises a hydrogenating component carried on a support. The principal ingredient of the hydrogenating component comprises a Group VIII metal or mixtures of Group VIII metals or their compounds. Examples of Group VIII metals which may be used as hydrogenating components are nickel, cobalt and iron. The metal should be present in an amount based on the catalyst composite between about 0.5 and 15%, preferably between 1 and 10 wt. Advantageously, a Group V1 metal or compound thereof may be used in conjunction with the Group VII metal as a hydrogenating component. Suitable Group Vl metals are molybdenum and tungsten. When the Group V1 metal is used it may be present in the catalyst in an amount between about 5 and 40% preferably between and wt. based on the catalyst composite. Examples of suitable hydrogenating components, the oxides of cobalt and molybdenum, the

oxides of nickel and molybdenum and the sulfides of ides are alumina, silica, magnesia, zirconia, beryllia, titania and the like. The support may also. comprise a crystalline alumino-silicate such as zeolite Y having a reduced alkali metal content e.g., less than 2%, more preferably less than 1 wt. alkali metal. The support may be composed entirely of the amorphous inorganic oxide or it may be composed of a mixture containing from 5 to about 60% zeolite of reduced alkali metal content. The catalyst may be used-as a slurry, a moving bed or a fixed bed. In a preferred embodiment, the catalyst is used in the form of a fixed bed of pellets having a maximum dimension of inch.

The hydrogen used in the hydrocracking step need not necessarily be pure but should have a purity of at least about 60% and more preferably between about and Electrolytic hydrogen, hydrogen obtained as a by product from catalytic reforming and hydrogen produced by the partial oxidation of a carbonaceous material followed by shift conversion and CO removal are satisfactory. The hydrogen may be introduced into about 1500 and 20,000 standard cubic foot per barrel of oil. Preferred conditions are a temperature between 725 and 850F., a pressure between 1300 and 3000 psig, a space velocity between 0.5 and 1.5 v/v/hr. and a hydrogen rate between 2000 and 10,000 scfb. The effluent from the hydrocracking zone is then passed to a high pressure separator for the removal of hydrogen which may be recycled to the hydrocracking zone, and the remainder is then fractionated to remove the hydrocarbon material boiling up to about 600F. leaving a lube oil fraction having an initial boiling point of about -600F. The lube oil fraction is then separated by fractional distillation into a light lube oil cut having a boiling range of about 600F. to 750F. and a heavy lube oil cut having an initial boiling point of about 750F.

The heavy lube oil out is then subjected to solvent extraction for the removal of aromatics using a solvent having an affinity for aromatic hydrocarbons. Particularly suitable solvents include furfural, phenol, sulfur dioxide and N-methyl-Z-pyrrolidone. Advantageously, the extraction is carried out using a countercurrent flow technique, the solvent being introduced at the top of an extraction tower and the oil near the bottom with the temperature in the tower being maintained at between about and 250F. The solvent to oil ratio may range between about 1 to 6 parts by volume of solvent per volume of oil. Oil of reduced aromatic content is recovered as raftinate from the top of the tower and is further processed by heating and steam stripping for removal of residual solvent. Solvent and extract are removed from the bottom of the extraction tower and may be separated by distillation.

The extract and the light lube oil cut are then combined and subjected to a catalytic hydrogenation treatment under relatively mild conditions such as a temperature between 625 and 800F., a pressure between 500 and 10,000 psig, a liquid hourly space velocity between 0.5 and 5.0 volumes of oil per volume of catalyst per hour in the presence of hydrogen introduced at a rate between 1000 and 10,000 scfb. Preferred conditions are a temperature between 675 and 800F., a pressure between 1500 and 2000 psig, a liquid hourly space velocity between 0.7 and 1.5 v/v/hr. and a hydrogen rate between 3,000 and 7000 scfb. Specific conditions are selected from the above ranges such that little if any, cracking takes place so that the lube oil yield from the hydrogenation step is at least about 90 volume and preferably about 95 volume Suitable catalysts'for the hydrogenation of the combined extract and light lube cut comprise metals or compounds of metals of Group VIII optionally used in conjunction with metals or compounds of metals of Group VI. Examples of Group VIII which may be used in this hydrogenation step are iron, cobalt, nickel, and noble metals such as platinum and palladium. Suitable Group VI metals are chromium, molybdenum and tungsten. Generally these components are supported on a relatively inert base, that is, one having little, if any, cracking activity. Suitable supports are refractory amorphous inorganic oxides such as alumina, silica, magnesia, zirconia, titania and the like. As in the hydrocracking step, the catalyst may be used in the form of a slurry or a moving bed or fixed bed of catalyst particles, the last being preferred. Particularly suitable catalysts are those containing from 0.2 to 2 wt. noble metal or from 1 to 10 wt. iron group metal. When a Group VI metal or compound thereof is used it should be present in an amount between about 5 and 30 wt. a preferred amount being between about 8 and 25 wt. Preferred catalysts are sulfided nickel-tungsten or cobalt molybdate or nickel molybdate supported on alumina preferably stabilized with a minor amount such as 1 to 10 wt. silica.

After separation of the hydrogen from the hydrogenation zone effluent, the hydrogenated oil may then be combined with the raffinate from the solvent extraction step and in a preferred embodiment, the combined stream is dewaxed although, if desired, the hydrogenated oil may be dewaxed separately from the raffinate.

De waxing effects a lowering of the pour point of the oil and may be accomplished by contacting the oil with a.-dewaxing agent such as a mixture of equal parts by volume of a ketone, for example, acetone or methyl ethyl ketone and an aromatic compound such as benzene or toluene using a ratio of about 3 to 4 parts by volume of solvent per volume of lubricating oil. The mixture is cooled to a temperature slightly below the desired pour point of the dewaxed oil which is ordinarily between about 0 and F. and the waxy components are removed from the chilled mixture by filtering or by centrifuging. The dewaxed liquid is then subjected to flash distillation and stripping to remove the solvent.

The following example is submitted for illustrative purposes only and it should not be construed that the invention is limited thereto.

EXAMPLE In this example the charge, a vacuum residuum (A), having an API gravity of 17.6", a viscosity SUS at 210F. of 474, a pour point of +F. and a carbon residue of 7.3 wt. is propane deasphalted at F. using a dosage of 770 vol. propane to yield a deasphalted vacuum residuum (B) having an API gravity of 224, a viscosity SUS at 210F. of 159.3, a pour point of 120+F. and a carbon residue of 1.97 wt. The deasphalted vacuum residuum is then hydrocracked by being passed downwardly at a temperature of 815F., a pressure of 1500 psig, a space velocity of 0.5 v/v/hr. with 2000 scfb hydrogen through a fixed bed of pelleted catalyst containing 2.3 wt. cobalt, 10.3 wt. molybdenum, 79.7 wt. alumina and 3.9 wt. silica and having a surface area of 290 m /g and a pore volume of 0.63 cc/g to produce a hydrocracked oil (c). The hydrocracked oil is separated from the unreacted hydrogen and low molecular weight hydrocarbons boiling up to about 600F. and is then fractionated into a 30% overhead light lube oil cut (D) and a 70% bottoms heavy lube oil cut (E). The heavy lube oil cut is then extracted with N-methyl-Z-pyrrolidone at a temperature of F. and a dosage of 100 volume to yield a raffinate (F) and an extract (G). The extract is combined with the light lube oil out (D) to produce a mixture (H) which is hydrogenated by being passed downwardly through a bed of pelleted catalyst composed of 5.9 wt. nickel and 18.3 wt. tungsten on alumina and having a surface area of 171 m /g at a temperature of 725F. a pressure of 1800 psig, a space velocity of 0.5 v/v/hr. with hydrogen at a rate of 7500 scfb. The lube oil portion and hydrogenated product (I) is recovered in a yield of 93.6% basis charge to the hydrogenation zone, is combined with the raffinate and the mixture (J) is dewaxed at a filtration temperature of 10F. to 15F. using as a solvent equal parts of methyl ethyl ketone and toluene to produce a dewaxed oil (K) having a pour point of 0F.

It will be appreciated that lube oil fractions are distilled under reduced pressure and the boiling range temperatures reported above are corrected to 760 mm. pressure.

In the following table the yields, the dewaxed viscosities, viscosity indices and pour points of the product of each step are reported. Also reported in the last line of the table are the same data for a procedure in which the same charge is deasphalted, hydrocracked, solvent refined and dewaxed without the fractionation and secondary hydrogenation.

Yield,\Vt% Dewaxed Visc, DEWAXED Basis A" SUS at 100F. VI POUR.F.

A. Resid charge 100 45 B. DA resid 80.0 7368 67 20 C. Hydrocracked B 60.7 289 104 5 D. 30 wt.% overhead ofC 18.2 179.5 46 0 E. 70 wt.% bottoms ofC 42.5 361 119 0 F. Solvent raffinate of E 34.0 364 132 0 G. Solvent extract of E 8.5 349 65 0 H. Combined extract and v overhead (D&G) 26.7 231 57 0 I. Hydrogenated H 25.1 210 82 0 J. Combined F&I 59.1 290 113 O K. Dewaxed .I 41.4 290 113 0 Conventional" 29 170.2 112 0 These data show the superior yields obtained by the process of our invention.

Although propane deasphalting a vacuum residuum prior to hydrocracking has been disclosed it is also possible to subject the charge prior to hydrocracking to a treatment such as solvent refining or deresining. It is also possible to dewax the hydrogenated mixture and the raftinate separately or together by a hydrocatalytic treatment whereby the oil to be dewaxed is passed into contact at elevated temperature and pressure with a catalyst comprising a hydrogenation component as described above supported on a mixture of an amorphous refractory inorganic oxide such as alumina, silica, zirconia, beryllia and the like composited with acidleached mordenite having a silicazalumina ratio of at least :1.

Obviously, various modifications of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be made as are indicated in the appended claims.

We claim:

1. A process for the production of lubricating oils which comprises hydrocracking heavy oil charge stock of which at least a portion boils above about 950F., recovering a lubricating oil fraction from the hydrocracked product, fractionating the lubricating oil fraction into a light lube oil cut and a heavy lube oil cut, contacting the heavy lube oil out with a solvent having an affinity for aromatics to produce an aromatic-poor raffinate and an aromatic-rich extract, combining the extract with said light lube oil cut and hydrogenating the resulting mixture.

2. The process of claim 1 in which the heavy oil charge is a wax distillate.

3. The process of claim 1 in which the heavy oil charge is a deasphalted residuum.

4. The process of claim 1 in which the light lube oil cut has a boiling range of about 600F. to 750F.

5. The process of claim 1 in which the light lube oil out amounts to between about 25 and 35% by volume of the hydrocracked lubricating oil fraction.

6. The process of claim 1 in which the hydrocracking temperature is higher than the hydrogenation temperature.

7. The process of claim 1 in which the solvent having an affinity for aromatics is furfural.

8. The process of claim 1 in which the solvent having an affinity for aromatics is N-mcthyl-Z-pyrrolidone.

9. The process of claim 1 in which the hydrogenated mixture of extract and light lube oil cut is combined with the raffinate and the resulting mixture is dewaxed. 

1. A PROCESS FOR THE PRODUCTION OF LUBRICATING OILS WHICH COMPRISES HYDROCRACKING HEAVY OIL CHARGE STOCK OF WHICH AT LEAST A PORTION BOILS ABOVE ABOUT 950*F., RECOVERING A LUBRICATING OIL FRACTION FROM THE HYDROCRACKED PRODUCT, FRACTIONATING THE LUBRICATING OIL FRACTION INTO A LIGHT LUBE OIL CUT AND A HEAVY LUBE OIL CUT, CONTACTING THE HEAVY LUBE OIL CUT WITH A SOLVENT HAVING AN AFFINITY FOR AROMATICS TO PRODUCE AN AROMATIC-POOR RAFFINATE AND AN AROMATIC-RICH EXTRACT, COMBINING THE EXTRACT WITH SAID LIGHT LUBE OIL CUT AND HYDROGENATING THE RESULTING MIXTURE.
 2. The process of claim 1 in which the heavy oil charge is a wax distillate.
 3. The process of claim 1 in which the heavy oil charge is a deasphalted residuum.
 4. The process of claim 1 in which the light lube oil cut has a boiling range of about 600*F. to 750*F.
 5. The process of claim 1 in which the light lube oil cut amounts to between about 25 and 35% by volume of the hydrocracked lubricating oil fraction.
 6. The process of claim 1 in which the hydrocracking temperature is higher than the hydrogenation temperature.
 7. The process of claim 1 in which the solvent having an affinity for aromatics is furfural.
 8. The process of claim 1 in which the solvent having an affinity for aromatics is N-methyl-2-pyrrolidone.
 9. The process of claim 1 in which the hydrogenated mixture of extract and light lube oil cut is combined with the raffinate and the resulting mixture is dewaxed. 